Electrophotographic photoconductor and aromatic polycarbonate resin for use therein

ABSTRACT

An electrophotographic photoconductor has an electroconductive support, and a photoconductive layer which is formed on the support and contains as an effective component an aromatic polycarbonate resin having a structural unit of formula (I), or the structural unit of formula (I) and a structural unit of formula (II):                    
     wherein Ar 1  to Ar 5 , R 1 , and X are as specified in the specification.

This application is a Division of 09/100,247 filed Jun. 19, 1998 nowU.S. Pat. No. 6,066,428.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrophotographic photoconductorcomprising an electroconductive support, and a photoconductive layerformed thereon, comprising an aromatic polycarbonate resin with chargetransporting properties. In addition, the present invention also relatesto the above-mentioned aromatic polycarbonate resin which is useful asthe material for the electrophotographic photoconductor.

2. Discussion of Background

Recently organic photoconductors (OPC) are used in many copying machinesand printers. The organic photoconductor has a layered structurecomprising a charge generation layer (CGL) and a charge transport layer(CTL) which are successively overlaid on an electroconductive support.The charge transport layer (CTL) is a film-shaped layer comprising abinder resin and a low-molecular-weight charge transport material (CTM)dissolved therein. The addition of such a low-molecular-weight chargetransport material (CTM) to the binder resin lowers the intrinsicmechanical strength of the binder resin, so that the CTL film is fragileand has a low tensile strength. Such lowering of the mechanical strengthof the CTL causes the wearing of the photoconductor or forms scratchesand cracks on the surface of the photoconductor.

Although some vinyl polymers such as polyvinyl anthracene, polyvinylpyrene and poly-N-vinylcarbazole have been studied ashigh-molecular-weight photoconductive materials for forming a chargetransporting complex for use in the conventional organic photoconductor,such polymers are not satisfactory from the viewpoint ofphotosensitivity.

In addition, high-molecular-weight materials having charge transportingproperties have been also studied to eliminate the shortcomings of theabove-mentioned layered photoconductor. For instance, there are proposedan acrylic resin having a triphenylamine structure as reported by M.Stolka et al., in “J. Polym. Sci., vol 21, 969 (1983)”; a vinyl polymerhaving a hydrazone structure as described in “Japan Hard Copy '89 p.67”; an aromatic polycarbonate resin having a benzidine structure asdisclosed in Japanese Laid-Open Patent Application 64-9964; andpolycarbonate resins having a triarylamine structure as disclosed inU.S. Pat. Nos. 4,801,517, 4,806,443, 4,806,444, 4,937,165, 4,959,288,5,030,532, 5,034,296, and 5,080,989, and Japanese Laid-Open PatentApplications Nos. 64-9964, 3-221522, 2-304456, 4-11627, 4-175337,4-18371, 4-31404, and 4-133065. However, any materials have not yet beenput to practical use.

According to the report of “Physical Review B46 6705 (1992)” by M. A.Abkowitz et al., it is confirmed that the drift mobility of ahigh-molecular weight charge transport material is lower than that of alow-molecular weight material by one figure. This report is based on thecomparison between the photoconductor comprising a low-molecular weighttetraarylbenzidine derivative dispersed in the photoconductive layer andthe one comprising a high-molecular polycarbonate having atetraarylbenzidine structure in its molecule. The reason for this hasnot yet been clarified, but this report suggests that the photoconductoremploying the high-molecular weight charge transport material producespoor results in terms of the photosensitivity and the residual potentialalthough the mechanical strength of the photoconductor is improved.

Conventionally known representative aromatic polycarbonate resins areobtained by allowing 2,2-bis(4-hydroxyphenyl)propane (hereinafterreferred to as bisphenol A) to react with phosgene or diphenylcarbonate.Such polycarbonate resins made from bisphenol A are used in many fieldsbecause of their excellent characteris-tics, such as high transparency,high heat resistance, high dimensional accuracy, and high mechanicalstrength.

For example, this kind of polycarbonate resin is intensively studied asa binder resin for use in the organic photoconductor in the field ofelectrophotography. A variety of aromatic polycarbonate resins have beenproposed as the binder resins for use in the charge transport layer ofthe layered photoconductor.

As previously mentioned, however, the mechanical strength of theaforementioned aromatic polycarbonate resin is decreased by the additionof the low-molecular-weight charge transport material in the chargetransport layer of the layered electrophotographic photoconductor.

SUMMARY OF THE INVENTION

It is therefore a first object of the present invention to provide anelectrophotographic photoconductor free from the conventionalshortcomings, which can show high photosensitivity and high durability.

A second object of the present intention is to provide an aromaticpolycarbonate resin that is remarkably useful as a high-molecular-weightcharge transport material for use in an organic electrophotographicphotoconductor.

The above-mentioned first object of the present invention can beachieved by an electrophotographic photoconductor comprising anelectroconductive support, and a photoconductive layer formed thereoncomprising as an effective component an aromatic polycarbonate resincomprising a structural unit of formula (I):

wherein Ar¹, Ar², Ar³ and Ar⁴ are each an arylene group which may have asubstituent; Ar⁵ is an aryl group which may have a substituent; and R¹is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which mayhave a substituent, or an aryl group which may have a substituent.

In the above-mentioned photoconductor, the structural unit of formula(I) may be represented by the following formula (III):

wherein Ar⁵ and R¹ are the same as those previously defined in formula(I).

Further, the structural unit of formula (II) may be represented byformula (IV):

The first object of the present invention can also be achieved by anelectrophotographic photoconductor comprising an electroconductivesupport, and a photoconductive layer formed thereon comprising as aneffective component an aromatic polycarbonate resin comprising theaforementioned structural unit of formula (I) and a structural unit ofthe following formula (II), with the composition ratio of the structuralunit of formula (I) to the structural unit of formula (II) satisfying arelationship of 0<k/(k+j)≦1, wherein k is the moiety ratio of thestructural unit of formula (I) and j is the moiety ratio of thestructural unit of formula (II):

wherein X is a bivalent aliphatic group, a bivalent cyclic aliphaticgroup, a bivalent aromatic group, a bivalent group obtained by bondingthe above-mentioned bivalent groups, or

in which R², R³, R⁴ and R⁵ are each independently an alkyl group whichmay have a substituent, an aryl group which may have a substituent, or ahalogen atom; a and b are each independently an integer of 0 to 4, c andd are each independently an integer of 0 to 3; and m is an integer of 0or 1, provided that when m=1, Y is a straight-chain alkylene grouphaving 2 to 12 carbon atoms, —O—, —S—, —SO—, —SO₂—, —CO—,

in which Z¹ and Z² are each a bivalent aliphatic group which may have asubstituent or an arylene group which may have a substituent, and R⁶,R⁷, R⁸, R⁹, R¹⁰, R¹¹ and R¹² are each independently a hydrogen atom, ahalogen atom, an alkyl group having 1 to 5 carbon atoms which nay have asubstituent, an alkoxyl group having 1 to 5 carbon atoms which may havea substituent, or an aryl group which may have a substituent, and R⁶ andR⁷ may form a carbocyclic ring or heterocyclic ring having 6 to 12carbon atoms together, or may form a carbocyclic ring or heterocyclicring in combination with R² and R³; p and q are each an integer of 0 or1, provided that when p and q represent 1, R¹² and R¹⁴ are each analkylene group having 1 to 4 carbon atoms; R¹⁵ and R¹⁶ are eachindependently an alkyl group having 1 to 5 carbon atoms which may have asubstituent, or an aryl group which may have a substituent; e is aninteger of 0 to 4; f is an integer of 0 to 20; and g is an integer of 0to 2000.

In the above-mentioned electrophotographic photoconductor, thestructural unit of formula (I) for use in the photoconductive layer maybe represented by the aforementioned structural unit of formula (III) or(IV).

The second object of the present invention can be achieved by anaromatic polycarbonate resin comprising a structural unit of formula(I):

wherein Ar¹, Ar², Ar³ and Ar⁴ are each an arylene group which may have asubstituent; Ar⁵ is an aryl group which may have a substituent; and R¹is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which mayhave a substituent, or an aryl group which may have a substituent.

In the above-mentioned polycarbonate resin, the structural unit offormula (I) may be represented by the above-mentioned formula (III), andpreferably by the formula (IV).

The second object of the present invention can also be achieved by anaromatic polycarbonate resin comprising the aforementioned structuralunits of formulas (I) and (II), with the composition ratio of thestructural unit of formula (I) to the structural unit of formula (II)satisfying a relationship of 0<k/(k+j)≦1, wherein k is the moiety ratioof the structural unit of formula (I) and j is the moiety ratio of thestructural unit of formula (II).

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic cross-sectional view of a first example of anelectrophotographic photoconductor according to the present invention.

FIG. 2 is a schematic cross-sectional view of a second example of anelectrophotographic photoconductor according to the present invention.

FIG. 3 is a schematic cross-sectional view of a third example of anelectrophotographic photoconductor according to the present invention.

FIG. 4 is a schematic cross-sectional view of a fourth example of anelectrophotographic photoconductor according to the present invention.

FIG. 5 is a schematic cross-sectional view of a fifth example of anelectrophotographic photoconductor according to the present invention.

FIG. 6 is a schematic cross-sectional view of a sixth example of anelectrophotographic photoconductor according to the present invention.

FIG. 7 is an IR spectrum of a diol compound synthesized in SynthesisExample 2, taken by use of a KBr tablet.

FIGS. 8 to 10 are IR spectra of aromatic polycarbonate resins accordingto the present invention, respectively synthesized in Examples 1-1 to1-3, taken by use of a thin-film.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The electrophotographic photoconductor according to the presentinvention comprises a photoconductive layer comprising:

(i) an aromatic polycarbonate resin comprising at least a structuralunit with the charge transporting properties, represented by formula(I), (III) or (IV),

(ii) an aromatic polycarbonate resin consisting of a structural unitwith the charge transporting properties, represented by formula (I),(III) or (IV), and

(iii) an aromatic polycarbonate copolymer resin comprising a structuralunit with the charge transporting properties, represented by formula(I), (III) or (IV), and a structural unit of formula (II) for impartingother properties than the charge transporting properties to the obtainedresin.

Those aromatic polycarbonate resins, which are novel compounds, havecharge transporting properties and high mechanical strength, so that theelectrical, optical and mechanical characteristics required for thecharge transport layer are satisfactory when those polycarbonate resinsare employed in the photoconductor of the present invention.

As previously mentioned, the aromatic polycarbonate resin of the presentinvention comprises the structural unit of formula (I):

wherein Ar¹, Ar², Ar³ and Ar⁴ are each an arylene group which may have asubstituent; Ar⁵ is an aryl group which may have a substituent; and R¹is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which mayhave a substituent, or an aryl group which may have a substituent.

It is preferable that the structural unit of formula (I) be representedby the following formula (III):

wherein Ar⁵ and R¹ are the same as those previously defined in formula(I).

Further, the structural unit of formula (III) may be represented byformula (IV):

Those aromatic polycarbonate resins according to the present inventioncan be obtained by the conventional synthesis method for thepolycarbonate resin, that is, polymerization of a bisphenol with acarbonic acid derivative.

To be more specific, the aromatic polycarbonate resin of the presentinvention can be produced by subjecting at least one diol compound withthe charge transporting properties, represented by the following formula(VI), (VII) or (VIII), and a halogenated carbonyl compound such asphosgene to interfacial polymerization.

wherein R¹ and Ar¹ to Ar⁵ are the same as those previously defined informula (I).

In addition to the phosgene, trichloromethyl chloroformate that is adimer of phosgene, and bis(trichloromethyl)carbonate that is a trimer ofphosgene are usable as the halogenated carbonyl compounds in theabove-mentioned interfacial polymerization. Further, halogenatedcarbonyl compounds derived from other halogen atoms than chlorine, forexample, carbonyl bromide, carbonyl iodide and carbonyl fluoride arealso employed.

The above-mentioned conventional synthesis method is described in thereference, such as “Handbook of Polycarbonate Resin” (issued by TheNikkan Kogyo Shimbun Ltd.).

When a diol of the following formula (IX) is employed in combinationwith the diol of formula (VI), (VII) or (VIII) with the chargetransporting properties in the course of the polymerization, there canbe produced a copolymer polycarbonate resin with improved mechanicalcharacteristics. In this case, a plurality of kinds of diol compoundsrepresented by formula (IX) may be employed.

OH—X—OH  (IX)

wherein X is the same as that previously defined in formula (II).

In such a synthesis method, the amount ratio of the diol represented byformula (VI), (VII) or (VIII) which is provided with the chargetransporting properties to the diol of formula (IX) can be selectedwithin a wide range in light of the desired characteristics of theobtained aromatic polycarbonate resin.

Further, a random copolymer polycarbonate resin can be obtainedaccording to the polymerization procedure. For instance, a randomcopolymer comprising the structural unit of formula (I), (III) or (IV)and the structural unit of formula (II) can be obtained when the diol offormula (VI), (VII) or (VIII) with the charge transporting propertiesand the diol of formula (IX) are uniformly mixed prior to thecondensation reaction with the phosgene.

The interfacial polymerization is carried out at the interface betweentwo phases of an alkaline aqueous solution of a diol and an organicsolvent which is substantially incompatible with water and capable ofdissolving a polycarbonate therein in the presence of the carbonic acidderivative and a catalyst. In this case, a polycarbonate resin with anarrow molecular-weight distribution can be speedily obtained byemulsifying the reactive medium through high-speed stirring operation oraddition of an emulsifying material.

As a base for preparing the alkaline aqueous solution, there can beemployed an alkali metal and an alkaline earth metal. Specific examplesof the base include hydroxides such as sodium hydroxide, potassiumhydroxide and calcium hydroxide; and carbonates such as sodiumcarbonate, potassium carbonate, calcium carbonate and sodiumhydrogencarbonate. Those bases may be used alone or in combination. Ofthose bases, sodium hydroxide and potassium hydroxide are preferable. Inaddition, distilled water or ion exchange water are preferably employedfor the preparation of the above-mentioned alkaline aqueous solution.

Examples of the organic solvent used in the above-mentioned interfacialpolymerization are aliphatic halogenated hydrocarbon solvents such asdichloromethane, 1,2-dichloroethane, 1,2-dichloroethylene,trichloro-ethane, tetrachloroethane and dichloropropane; aromatichalogenated hydrocarbon solvents such as chlorobenzene anddichlorobenzene; and mixed solvents thereof. Further, aromatichydrocarbon solvents such as toluene, xylene and ethylbenzene, oraliphatic hydrocarbon solvents such as hexane and cyclohexane may beadded to the above-mentioned solvents. Of those organic solvents, thealiphatic halogenated hydrocarbon solvents and aromatic halogenatedhydrocarbon solvents, in particular, dichloromethane and chlorobenzeneare preferable in the present invention.

Examples of the catalyst used in the preparation of the polycarbonateresin are a tertiary amine, a quaternary ammonium salt, a tertiaryphosphine, a quaternary phosphonium salt, a nitrogen-containingheterocyclic compound and salts thereof, an iminoether and saltsthereof, and a compound having amide group.

Specific examples of such a catalyst used in the interracialpolymerization include trimethylamine, triethylamine, tri-n-propylamine,tri-n-hexylamine, N,N,N′,N′-tetramethyl-1,4-tetranethylenediamine,4-pyrrolidinopyridine, N,N′-dimethylpiperazine, N-ethylpiperidine,benzyltrimethylammonium chloride, benzyltriethylammonium chloride,tetramethylammonium chloride, tetraethylazmonium bromide,phenyltriethylammonium chloride, triethylphosphine, triphenylphosphine,diphenylbutylphosphine, tetra(hydroxymethyl)phosphonium chloride,benzyltriethylphosphonium chloride, benzyltriphenylphosphonium chloride,4-methylpyridine, 1-methylimidazole, 1,2-dimethylimidazole,3-methylpyridazine, 4,6-dimethylpyrimidine,1-cyclohexyl-3,5-dimethylpyrazole, and 2,3,5,6-tetramethylpyrazine.

Those catalysts may be used alone or in combination. Of theabove-mentioned catalysts, the tertiary amine, in particular, a tertiaryamine having 3 to 30 carbon atoms, such as triethylamine is preferablyemployed in the present invention. Before and/or after the carbonic acidderivatives such as phosgene and bischloroformate are placed in thereaction system, any of the above-mentioned catalysts may be addedthereto.

To control the molecular weight of the obtained polycarbonate resin, itis desirable to employ a terminator as a molecular weight modifier forany of the above-mentioned polymerization reactions. Consequently, asubstituent derived from the terminator may be bonded to the end of themolecule of the obtained polycarbonate resin.

As the terminator for use in the present invention, a monovalentaromatic hydroxy compound and haloformate derivatives thereof, and amonovalent carboxylic acid and halide derivatives thereof can be usedalone or in combination.

Specific examples of the monovalent aromatic hydroxy compound includephenols such as phenol, p-cresol, o-ethylphenol, p-ethylphenol,p-isopropylphenol, p-tert-butylphenol, p-cumylphenol,p-cyclohexylphenol, p-octylphenol, p-nonylphenol, 2,4-xylenol,p-methoxyphenol, p-hexyloxyphenol, p-decyloxyphenol, o-chlorophenol,m-chlorophenol, p-chlorophenol, p-bromophenol, pentabromophenol,pentachlorophenol, p-phenylphenol, p-isopropenylphenol,2,4-di(1′-methyl-1′-phenylethyl)-phenol, β-naphthol, α-naphthol,p-(2′,4′,4′-trimethyl-chromanyl)phenol, and2-(4′-methoxyphenyl)-2-(4″-hydroxyphenyl)propane. In addition, alkalimetal salts and alkaline earth metal salts of the above phenols can alsobe employed.

Specific examples of the monovalent carboxylic acid include aliphaticacids such as acetic acid, propionic acid, butyric acid, valeric acid,caproic acid, heptanic acid, caprylic acid, 2,2-dimethylpropionic acid,3-methylbutyric acid, 3,3-dimethylbutyric acid, 4-methylvaleric acid,3,3-dimethylvaleric acid, 4-methylcaproic acid, 3,5-dimethylcaproic acidand phenoxyacetic acid; and benzoic acids such as p-methylbenzoic acid,p-tert-butylbenzoic acid, p-butoxybenzoic acid, p-octyloxybenzoic acid,p-phenylbenzoic acid, p-benzylbenzoic acid and p-chlorobenzoic acid. Inaddition, alkali metal salts and alkaline earth metal salts of theabove-mentioned aliphatic acids and benzoic acids can also be employedas the terminators. Of those terminators, the monovalent aromatichydroxy compound, in particular, phenol, p-tert-butylphenol, orp-cumylphenol is preferable.

It is preferable that the thus obtained aromatic polycarbonate resin foruse in the photoconductor of the present invention have a number-averagemolecular weight of 1,000 to 500,000, more preferably in the range of10,000 to 200,000 when expressed by the styrene-reduced value.

Furthermore, a branching agent may be added in a small amount during thepolymerization in order to improve the mechanical properties of theobtained polycarbonate resin. Any compounds that have three or morereactive groups, which may be the same or different, selected from thegroup consisting of an aromatic hydroxyl group, a haloformate group, acarboxylic acid group, a carboxylic acid halide group, and an activehalogen atom can be used as the branching agent for use in the presentinvention.

Specific examples of the branching agent for use in the presentinvention are as follows:

phloroglucinol,

4,6-dimethyl-2,4,6-tris(4′-hydroxyphenyl)-2-heptene,

4,6-dimethyl-2,4,6-tris (4′-hydroxyphenyl)heptane,

1,3,5-tris(4′-hydroxyphenyl)benzene,

1,1,1-tris(4′-hydroxyphenyl)ethane,

1,1,2-tris(4′-hydroxyphenyl)propane,

α,α,α′-tris(4′-hydroxyphenyl)-1-ethyl-4-isopropylbenzene,

2,4-bis[α-methyl-α-(4′-hydroxyphenyl) ethyl]phenol,

2-(4′-hydroxyphenyl)-2-(2″,4″-dihydroxyphenyl)propane,

tris(4-hydroxyphenyl) phosphine,

1,1,4,4-tetrakis(4′-hydroxyphenyl)cyclohexane,

2,2-bis[4′,4′-bis (4″-hydroxyphenyl)cyclohexyl]-propane,

α,α,α′,α′-tetrakis(4′-hydroxyphenyl)-1,4-diethylbenzene,

2,2,5,5-tetrakis(4′-hydroxyphenyl)hexane,

1,1,2,3-tetrakis(4′-hydroxyphenyl)propane,

1,4-bis(4′,4″-dihydroxytriphenylmethyl)benzene,

3,3′,5,5′-tetrahydroxydiphenyl ether,

3,5-dihydroxybenzoic acid,

3,5-bis(chlorocarbonyloxy)benzoic acid,

4-hydroxyisophthalic acid,

4-chlorocarbonyloxyisophthalic acid,

5-hydroxyphthalic acid,

5-chlorocarbonyloxyphthalic acid,

trimesic trichloride, and

cyanuric chloride.

Those branching agents may be used alone or in combination.

To prevent the oxidation of the diol in the alkaline aqueous solution,an antioxidant such as hydrosulfite may be used for the interfacialpolymerization reaction.

The interfacial polymerization reaction is generally carried out attemperature in the range of 0 to 40° C., and terminated in severalminutes to 5 hours. It is desirable to maintain the reaction system topH 10 or more.

The polycarbonate resin thus synthesized is purified by removing thecatalyst and the antioxidant used in the polymerization; unreacted dialand terminator; and impurities such as an inorganic salt generatedduring the polymerization, and then subjected to the preparation of thephotoconductive layer of the electrophotographic photoconductoraccording to the present invention. The previously mentioned “Handbookof Polycarbonate Resin” (issued by Nikkan Kogyo Shimbun Ltd.) can bereferred to for such a procedure for purifying the polycarbonate resin.

To the aromatic polycarbonate resin produced by the previously mentionedmethod, various additives such as an antioxidant, a light stabilizer, athermal stabilizer, a lubricant and a plasticizer can be added whennecessary.

The structural unit of formula (I) for use in the polycarbonate resinaccording to the present invention will now be explained in detail.

Ar¹, Ar², Ar³ and Ar⁴ in the formula (I) represent a substituted orunsubstituted arylene group, which is derived from a substituted orunsubstituted aryl group.

Examples of the aryl group from which the above-mentioned arylene groupis derived are phenyl group, naphthyl group, biphenylyl group,terphenylyl group, pyrenyl group, fluorenyl group,9,9-dimethyl-2-fluorenyl group, azulenyl group, anthryl group,triphenylenyl group, chrysenyl group, fluorenylidenephenyl group,5H-dibenzo[a,d]cycloheptenylidenephenyl group, thienyl group,benzothienyl group, furyl group, benzofuranyl group, carbazolyl group,pyridinyl group, pyrrolidyl group, and oxazolyl group.

Examples of the substituent for the above-nentioned aryl group includean alkyl group, an alkoxyl group, a halogen atom such as fluorine atom,chlorine atom, bromine atom or iodine atom, and an amino grouprepresented by the following formula (X):

in which R¹⁹ and R²⁰ are each an alkyl group which may have asubstituent, or an aryl group which may have a substituent, and R¹⁹ andR²⁰ may form a ring together, or in combination with the carbon atom ofthe aryl group. Namely, there can be employed piperidino group,morpholino group, and julolidyl group.

Examples of the alkyl group represented by R¹⁹ and R²⁰ include astraight-chain or branched alkyl group having 1 to 5 carbon atoms. Theabove alkyl group may have a substituent such as a fluorine atom, cyanogroup, or a phenyl group which may have a substituent selected from thegroup consisting of a halogen atom and a straight-chain or branchedalkyl group having 1 to 5 carbon atoms.

Specific examples of the above alkyl group include methyl group, ethylgroup, n-propyl group, isopropyl group, tert-butyl group, sec-butylgroup, n-butyl group, isobutyl group, trifluoromethyl group,2-cyanoethyl group, benzyl group, 4-chlorobenzyl group, and4-methylbenzyl group.

As the substituted or unsubstituted aryl group represented by R¹⁹ andR²⁰, the same examples of the substituted or unsubstituted aryl group asthose defined in the description of the arylene group represented byAr¹, Ar², Ar³ and Ar⁴.

Ar⁵ in formula (I) represents an aryl group which may have asubstituent.

Examples of the aryl group represented by Ar⁵ include a monovalent groupderived from a heterocyclic group having an amine structure therein,such as a group represented by the following formula (XI), pyrrole,pyrazole, imidazole, triazole, dioxazole, indole, isoindole,benzimidazole, benzotriazole, benzoisoxazine, carbazole, andphenoxazine. Such an aryl group may have a substituent, for example, thesame substituted or unsubstituted alkyl group as defined in thedescription of R¹⁹ and R²⁰, the same substituted or unsubstituted arylgroup as defined in the description of the arylene group represented byAr¹ to Ar⁴, and a halogen atom such as fluorine atom, chlorine atom,bromine atom or iodine atom.

The above-mentioned group represented by formula (XI) is as follows:

wherein R²¹ and R²² are each an acyl group, an alkyl group which mayhave a substituent, or an aryl group which may have a substituent; Ar⁶is an arylene group; and h is an integer of 1 to 3.

In the aforementioned formula (XI), examples of the acyl grouprepresented by R²¹ and R²² are acetyl group, propionyl group, andbenzoyl group. As the alkyl group represented by R²¹ and R²², the sameexamples of the substituted or unsubstituted alkyl group as defined inthe description of R¹⁹ and R²⁰ can be employed.

As the aryl group represented by R²¹ and R²², there can be employed thesame examples of the substituted or unsubstituted aryl group from whichthe substituted or unsubstituted arylene group can be derived, asdefined in the description of Ar¹ to Ar⁴, and a group represented by thefollowing formula (XII):

wherein R²³ is a hydrogen atom, the same substituted or unsubstitutedalkyl group as defined in the description of R¹⁹ and R²⁰, an alkoxylgroup, a halogen atom, the same substituted or unsubstituted aryl groupfrom which the arylene group is derived as defined in the description ofAr¹ to Ar⁴, amino group, nitro group or cyano group; and B is —O—, —S—,—SO—, —SO₂—, —CO—, or the following bivalent groups:

in which R²⁴ is a hydrogen atom, the same substituted or unsubstitutedalkyl group as defined in the description of R¹⁹ and R²⁰, or the samesubstituted or unsubstituted aryl group from which the arylene group isderived as defined in the description of Ar¹ to Ar⁴; i is an integer of1 to 12; and j is an integer of 1 to 3.

Specific examples of the alkoxyl group represented by R²³ are methoxygroup, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group,isobutoxy group, s-butoxy group, t-butoxy group, 2-hydroxyethoxy group,2-cyanoethoxy group, benzyloxy group, 4-methylbenzyloxy group andtrifluoromethoxy group.

Specific examples of the halogen atom represented by R²³ are fluorineatom, chlorine atom, bromine atom and iodine atom.

As the amino group represented by R²³, there can be employed thepreviously mentioned amino group of formula (X) as defined in thedescription of the substituent of Ar¹ to Ar⁴.

As the arylene group represented by Ar⁶ in formula (XI), there can beemployed the same examples of the substituted or unsubstituted arylenegroup represented by Ar¹ to Ar⁴.

R¹ in formula (I) is a hydrogen atom, a substituted or unsubstitutedalkyl group or a substituted or unsubstituted aryl group.

As the aryl group represented by R¹, there can be employed the sameexamples of the substituted or unsubstituted aryl group represented byAr⁵.

In other formulas than the formula (I), the same examples as defined inthe description of formula (I) can be employed so long as the symbolsuch as Ar¹ or R¹ for use in the formula is identical.

In the present invention, there can be provided the aromaticpolycarbonate resin of formula (I), preferably the polycarbonate resinof formula (III), more preferably that of formula (IV), and furtherpreferably that of the following formula (V):

The diol of formula (VI), (VII) or (VIII) serving as the raw materialmonomer for the aromatic polycarbonate resin of the present invention isa novel compound.

For example, the diol of formula (VI) can be synthesized by allowing adiol of formula (XV), which is disclosed in Japanese Patent Application7-323268, to react with compounds of formulas (XVI) and (XVII) toproduce an ether compound represented by formula (XVIII) and carryingout the cleavage of ester groups in the ether compound of formula(XVIII) in accordance with the following reaction scheme:

wherein R²⁵ and R²⁶ are each an alkyl group which may have asubstituent; R²⁷ and R²⁸ are each a halogen atom; Ar¹, Ar², Ar³, Ar⁴,Ar⁵ and R¹ are the same as those previously defined.

In the above reaction scheme, the stilbene compounds of formulas (XVIII)and (VI), which serve as the intermediates for the preparation of thearomatic polycarbonate resin of the present invention, are novelcompounds.

According to the present invention, the polycarbonate resin for use inthe photoconductive layer of the electrophotographic photoconductorcomprises the structural unit of formula (I) which is provided with thecharge transporting properties. To control the mechanicalcharacteristics of the obtained polycarbonate resin, the polycarbonateresin in the form of a copolymer can be prepared by using the structuralunit of formula (I) and the structural unit for use in the conventionalpolycarbonate resins, for example, as described in the previouslymentioned “Handbook of Polycarbonate Resin” (issued by The Nikkan KogyoShimbun Ltd.). The previously mentioned structural unit of formula (II),which is one of the structural units for use in the conventionalpolycarbonate resins, can be preferably employed in combination with thestructural unit of formula (I) in the present invention.

The structural unit of formula (II) will now be explained by referringto the diol of formula (IX) that is the starting material for thestructural unit of formula (II).

HO—X—OH  (IX)

In the case where X in the diol of formula (IX) represents a bivalentaliphatic group or bivalent cyclic aliphatic group, the representativeexamples of the obtained diol are as follows: ethylene glycol,diethylene glycol, triethylene glycol, polyethylene glycol,polytetramethylene ether glycol, 1,3-propanediol, 1,4-butanediol,1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol,1,5-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, neopentyl glycol,2-ethyl-1,6-hexanediol, 2-methyl-1,3-propanediol,2-ethyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol,1,3-cyclohexanediol, 1,4-cyclohexanediol, cyclohexane-1,4-dimethanol,2,2-bis(4-hydroxycyclohexyl)propane, xylylenediol,1,4-bis(2-hydroxyethyl)benzene, 1,4-bis(3-hydroxypropyl)benzene,1,4-bis(4-hydroxybutyl)benzene, 1,4-bis(5-hydroxypentyl)benzene, and1,4-bis(6-hydroxyhexyl)benzene.

In the case where X in the diol of formula (IX) represents a bivalentaromatic group, there can be employed any bivalent groups derived fromthe substituted or unsubstituted aryl group as defined in thedescription of Ar¹, Ar², Ar³ and Ar⁴.

In addition, X represents the following bivalent groups;

in which R², R³, R⁴ and R⁵ are each independently an alkyl group whichmay have a substituent, an aryl group which may have a substituent, or ahalogen atom; a and b are each independently an integer of 0 to 4; c andd are each independently an integer of 0 to 3; and m is an integer of 0or 1, provided that when m=1, Y is a straight-chain alkylene grouphaving 2 to 12 carbon atoms, —O—, —S—, —SO—, —SO₂—, —CO—,

in which Z¹ and Z² are each a bivalent aliphatic group which may have asubstituent or an arylene group which may have a substituent; and R⁶,R⁷, R⁸, R⁹, R¹⁰, R¹¹ and R¹² are each independently a hydrogen atom, ahalogen atom, an alkyl group having 1 to 5 carbon atoms which may have asubstituent, an alkoxyl group having 1 to 5 carbon atoms which may havea substituent, or an aryl group which may have a substituent, and R⁶ andR⁷ may form a carbocyclic ring or heterocyclic ring having 6 to 12carbon atoms together, or may form a carbocyclic ring or heterocyclicring in combination with R² and R³; p and q are each an integer of 0 or1, provided that when p and q represent 1, R¹³ and R¹⁴ are each analkylene group having 1 to 4 carbon atoms; R¹⁵ and R¹⁶ are eachindependently an alkyl group having 1 to 5 carbon atoms which may have asubstituent, or an aryl group which may have a substituent; e is aninteger of 0 to 4; f is an integer of 0 to 20; and g is an integer of 0to 2000.

In the above-mentioned bivalent groups, the same substituted orunsubstituted alkyl group as defined in the description of R¹⁹ and R²⁰,and the same substituted or unsubstituted aryl group as defined in thedescription of Ar¹, Ar², Ar³ and Ar⁴ can be employed.

Examples of the halogen atom in the above bivalent groups include afluorine atom, a chlorine atom, a bromine atom and an iodine atom.

When Z¹ and Z² each represents a substituted or unsubstituted bivalentaliphatic group, there can be employed any bivalent groups obtained byremoving the hydroxyl groups from the diol of formula (IX) in which Xrepresents a bivalent aliphatic group or a bivalent cyclic aliphaticgroup. On the other hand, when Z¹ and Z² each represents a substitutedor unsubstituted arylene group, there can be employed any bivalentgroups derived from the substituted or unsubstituted aryl group aspreviously defined in the description of Ar¹, Ar², Ar³ and Ar⁴.

Preferable examples of the diol of formula (IX) in which X represents abivalent aromatic group are as follows:

bis(4-hydroxyphenyl)methane,

bis(2-methyl-4-hydroxyphenyl) methane,

bis(3-methyl-4-hydroxyphenyl)methane,

1,1-bis(4-hydroxyphenyl)ethane,

1,2-bis(4-hydroxyphenyl)ethane,

bis(4-hydroxyphenyl)phenylmethane,

bis(4-hydroxyphenyl)diphenylmethane,

1,1-bis(4-hydroxyphenyl)-1-phenylethane,

1,3-bis(4-hydroxyphenyl)-1,1-dimethylpropane,

2,2-bis(4-hydroxyphenyl)propane,

2-(4-hydroxyphenyl)-2-(3-hydroxyphenyl)propane,

1,1-bis(4-hydroxyphenyl)-2-methylpropane,

2,2-bis(4-hydroxyphenyl)butane,

1,1-bis(4-hydroxyphenyl)-3-methylbutane,

2,2-bis(4-hydroxyphenyl)pentane,

2,2-bis(4-hydroxyphenyl)-4-methylpentane,

2,2-bis(4-hydroxyphenyl)hexane,

4,4-bis(4-hydroxyphenyl)heptane,

2,2-bis(4-hydroxyphenyl)nonane,

bis(3,5-dimethyl-4-hydroxyphenyl) methane,

2,2-bis(3-methyl-4-hydroxyphenyl)propane,

2,2-bis(3-isopropyl-4-hydroxyphenyl)propane,

2,2-bis(3-sec-butyl-4-hydroxyphenyl)propane,

2,2-bis(3-tert-butyl-4-hydroxyphenyl)propane,

2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane,

2,2-bis(3-allyl-4-hydroxyphenyl)propane,

2,2-bis(3-phenyl-4-hydroxyphenyl) propane,

2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane,

2,2-bis(3-chloro-4-hydroxyphenyl)propane,

2,2-bis(3,5-dichloro-4-hydroxyphenyl) propane,

2,2-bis(3-bromo-4-hydroxyphenyl)propane,

2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane,

2,2-bis(4-hydroxyphenyl)hexafluoropropane,

1,1-bis(4-hydroxyphenyl)cyclopentane,

1,1-bis(4-hydroxyphenyl) cyclohexane,

1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane,

1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclohexane,

1,1-bis(3,5-dichloro-4-hydroxyphenyl)cyclohexane,

1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane,

1,1-bis(4-hydroxyphenyl)cycloheptane,

2,2-bis(4-hydroxyphenyl)norbornane,

2,2-bis(4-hydroxyphenyl)adamantane,

4,4′-dihydroxydiphenyl ether,

4,4′-dihydroxy-3,3′-dimethyldiphenyl ether,

ethylene glycol bis(4-hydroxyphenyl)ether,

4,4′-dihydroxydiphenylsulfide,

3,3′-dimethyl-4,4′-dihydroxydiphenylsulfide,

3,3′,5,5′-tetramethyl-4,4′-dihydroxydiphenylsulfide,

4,4′-dihydroxydiphenylsulfoxide,

3,3′-dimethyl-4,4′-dihydroxydiphenylsulfoxide,

4,4′-dihydroxydiphenylsulfone,

3,3′-dimethyl-4,4′-dihydroxydiphenylsulfone,

3,3′-diphenyl-4,4′-dihydroxydiphenylsulfone,

3,3′-dichloro-4,4′-dihydroxydiphenylsulfone,

bis(4-hydroxyphenyl)ketone,

bis(3-methyl-4-hydroxyphenyl)ketone,

3,3,3′,3′-tetramethyl-6,6′-dihydroxyspiro(bis)indane,

3,3′,4,4′-tetrahydro-4,4,4′,4′-tetramethyl-2,2′-spirobi(2H-1-benzopyrane-7,7′-diol,

trans-2,3-bis(4-hydroxyphenyl)-2-butene,

9,9-bis(4-hydroxyphenyl)fluorene,

9,9-bis(4-hydroxyphenyl)xanthene,

1,6-bis(4-hydroxyphenyl)-1,6-hexanedione,

α,α,α′,α′-tetramethyl-α,α′-bis(4-hydroxyphenyl)-p-xylene,

α,α,α′,α′-tetramethyl-α,α′-bis(4-hydroxyphenyl)-m-xylene,

2,6-dihydroxydibenzo-p-dioxine,

2,6-dihydroxythianthrene,

2,7-dihydroxyphenoxathine,

9,10-dimethyl-2,7-dihydroxyphenazine,

3,6-dihydroxydibenzofuran,

3,6-dihydroxydibenzothiophene,

4,4′-dihydroxybiphenyl,

1,4-dihydroxynaphthalene,

2,7-dihydroxypyrene,

bydroquinone,

resorcin,

ethylene glycol-bis(4-hydroxybenzoate),

diethylene glycol-bis(4-hydroxybenzoate),

triethylene glycol-bis(4-hydroxybenzoate),

1,3-bis(4-hydroxyphenyl)-tetramethyldisiloxane, and

phenol-modified silicone oil.

Further, an aromatic diol having an ester linkage produced by thereaction between 2 moles of a diol and one mole of isophthaloyl chlorideor terephthaloyl chloride is also usable.

In the polycarbonate copolymer resin comprising the structural unit offormula (I) and the structural unit of formula (II), the molar ratio ofa moiety composed of the structural unit of formula (I) may be freelydetermined, but preferably 5 mol % or more, more preferably 20 mol % ormore with respect to the total amount of the polycarbonate resin becausethe content of the structural unit of formula (I) has an effect on thecharge transporting properties of the obtained polycarbonate resin.

In the photoconductors according to the present invention, at least oneof the previously mentioned aromatic polycarbonate resins is containedin the photoconductive layers 2, 2 a, 2 b, 2 c, 2 d, and 2 e. Thearomatic polycarbonate resin can be employed in different ways, forexample, as shown in FIGS. 1 through 6.

In the photoconductor as shown in FIG. 1, a photoconductive layer 2 isformed on an electroconductive support 1, which photoconductive layer 2comprises an aromatic polycarbonate resin of the present invention and asensitizing dye, with the addition thereto of a binder agent (binderresin) when necessary. In this photo-conductor, the aromaticpolycarbonate resin works as a photoconductive material, through whichcharge carriers necessary for the light decay of the photoconductor aregenerated and transported. However, the aromatic polycarbonate resinitself scarcely absorbs light in the visible light range, and therefore,it is necessary to add a sensitizing dye which absorbs light in thevisible light range in order to form latent electrostatic images by useof visible light.

Referring to FIG. 2, there is shown an enlarged cross-sectional view ofanother embodiment of an electrophotographic photoconductor according tothe present invention. In this photoconductor, there is formed aphotoconductive layer 2 a on an electroconductive support 1. Thephotoconductive layer 2 a comprises a charge transport medium 4′comprising (i) an aromatic polycarbonate resin of the present invention,optionally in combination with a binder agent, and (ii) a chargegeneration material 3 dispersed in the charge transport medium 4′. Inthis embodiment, the aromatic poly-carbonate resin (or a mixture of thearomatic poly-carbonate resin and the binder agent) constitutes thecharge transport medium 4′. The charge generation material 3, which is,for example, an inorganic material or an organic pigment, generatescharge carriers. The charge transport medium 4′ accepts the chargecarriers generated by the charge generation material 3 and transportsthose charge carriers.

In this electrophotographic photoconductor, it is basically necessarythat the light-absorption wavelength regions of the charge generationmaterial 3 and the aromatic polycarbonate resin not overlap in thevisible light range. This is because, in order that the chargegeneration material 3 produce charge carriers efficiently, it isnecessary that light pass through the charge transport medium 4′ andreach the surface of the charge generation material 3. Since thearomatic polycarbonate resin comprising the structural unit of formula(I) do not substantially absorb light with a wavelength of 600 nm ormore, it can work effectively as the charge transport material when usedin combination with the charge generation material 3 which can absorbthe light in the visible region to the near infrared region and generatecharge carriers. The charge transport medium 4′ may further comprise alow-molecular weight charge transport material.

Referring to FIG. 3, there is shown an enlarged cross-sectional view ofa further embodiment of an electrophotographic photoconductor accordingto the present invention. In the figure, there is formed on anelectroconductive support 1 a two-layered photoconductive layer 2 bcomprising a charge generation layer 5 containing the charge generationmaterial 3, and a charge transport layer 4 comprising an aromaticpolycarbonate resin with the charge transporting properties according tothe present invention.

In this photoconductor, light which has passed through the chargetransport layer 4 reaches the charge generation layer 5, and chargecarriers are generated within the charge generation layer 5. The chargecarriers which are necessary for the light decay for latentelectrostatic image formation are generated by the charge generationmaterial 3, and accepted and transported by the charge transport layer4. The generation and transportation of the charge carriers areperformed by the same mechanism as that in the photo-conductor shown inFIG. 2.

In this case, the charge transport layer 4 comprises the aromaticpolycarbonate resin, optionally in combination with a binder agent. Inorder to increase the efficiency of generating the charge carriers, thecharge generation layer 5 may further comprise the aromaticpolycarbonate resin of the present invention. Furthermore, thephotoconductive layer 2 b including the charge generation layer 5 andthe charge transport layer 4 may further comprise a low-molecular weightcharge transport material. This can be applied to the embodiments ofFIGS. 4 to 6 to be described later.

In the electrophotographic photoconductor of FIG. 3, a protective layer6 may be provided on the charge transport layer 4 as shown in FIG. 4.The protective layer 6 may comprise the aromatic polycarbonate resin ofthe present invention, optionally in combination with a binder agent. Insuch a case, it is effective that the protective layer 6 be provided ona charge transport layer in which a low-molecular weight chargetransport material is dispersed. The protective layer 6 may be providedon the photoconductive layer 2 a of the photoconductor as shown in FIG.2.

Referring to FIG. 5, there is shown still another embodiment of anelectrophotographic photoconductor according to the present invention.In this figure, the overlaying order of the charge generation layer 5and the charge transport layer 4 comprising the aromatic poly-carbonateresin is reversed in view of the electrophoto-graphic photoconductor asshown in FIG. 3. The mechanism of the generation and transportation ofcharge carriers is substantially the same as that of the photoconductorshown in FIG. 3.

In the above photoconductor of FIG. 5, a protective layer 6 may beformed on the charge generation layer 5 as shown in FIG. 6 in light ofthe mechanical strength of the photoconductor.

When the electrophotographic photoconductor according to the presentinvention as shown in FIG. 1 is fabricated, at least one aromaticpolycarbonate resin of the present invention is dissolved in a solvent,with the addition thereto of a binder agent when necessary. To the thusprepared solution, a sensitizing dye is added, so that a photoconductivelayer coating liquid is prepared. The thus prepared photoconductivelayer coating liquid is coated on an electroconductive support 1 anddried, so that a photoconductive layer 2 is formed on theelectroconductive support 1.

It is preferable that the thickness of the photo-conductive layer 2 bein the range of 3 to 50 μm, more preferably in the range of 5 to 40 μm.

It is preferable that the amount of aromatic polycarbonate resin of thepresent invention be in the range of 30 to 100 wt. % of the total weightof the photoconductive layer 2. It is preferable that the amount ofsensitizing dye for use in the photoconductive layer 2 be in the rangeof 0.1 to 5 wt. %, more preferably in the range of 0.5 to 3 wt. % of thetotal weight of the photoconductive layer 2.

Specific examples of the sensitizing dye for use in the presentinvention are triarylmethane dyes such as Brilliant Green, Victoria BlueB, Methyl Violet, Crystal Violet and Acid Violet 6B; xanthene dyes suchas Rhodamine B, Rhodamine 6G, Rhodamine G Extra, Eosin S, Erythrosin,Rose Bengale and Fluoresceine; thiazine dyes such as Methylene Blue; andcyanine dyes such as cyanin.

The electrophotographic photoconductor shown in FIG. 2 can be fabricatedby the following method:

The finely-divided particles of the charge generation material 3 aredispersed in a solution in which at least one aromatic polycarbonateresin of the present invention, or a mixture of the aromaticpolycarbonate resin and the binder agent is dissolved, so that a coatingliquid for the photoconductive layer 2 a is prepared. The coating liquidthus prepared is coated on the electroconductive support 1 and thendried, whereby the photoconductive layer 2 a is provided on theelectroconductive support 1.

It is preferable that the thickness of the photoconductive layer 2 a bein the range of 3 to 50 μm, more preferably in the range of 5 to 40 μm.

It is preferable that the amount of aromatic polycarbonate resin withthe charge transporting properties be in the range of 40 to 100 wt. % ofthe total weight of the photoconductive layer 2 a. It is preferable thatthe amount of charge generation material 3 for use in thephotoconductive layer 2 a be in the range of 0.1 to 50 wt. %, morepreferably in the range of 1 to 20 wt. % of the total weight of thephotoconductive layer 2 a.

Specific examples of the charge generation material 3 for use in thepresent invention are as follows: inorganic materials such as selenium,selenium—tellurium, cadmium sulfide, cadmium sulfide—selenium andα-silicon (amorphous silicon); and organic pigments, for example, azopigments, such as C.I. Pigment Blue 25 (C.I. 21180), C.I. Pigment Red 41(C.I. 21200), C.I. Acid Red 52 (C.I. 45100), C.I. Basic Red 3 (C.I.45210), an azo pigment having a carbazole skeleton (Japanese Laid-OpenPatent Application 53-95033), an azo pigment having a distyryl benzeneskeleton (Japanese Laid-Open Patent Application 53-133445), an azopigment having a triphenylamine skeleton (Japanese Laid-Open PatentApplication 53-132347), an azo pigment having a dibenzothiopheneskeleton (Japanese Laid-Open Patent Application 54-21728), an azopigment having an oxadiazole skeleton (Japanese Laid-Open PatentApplication 54-12742), an azo pigment having a fluorenone skeleton(Japanese Laid-Open Patent Application 54-22834), an azo pigment havinga bisstilbene skeleton (Japanese Laid-Open Patent Application 54-17733),an azo pigment having a distyryl oxadiazole skeleton (Japanese Laid-OpenPatent Application 54-2129), and an azo pigment having a distyrylcarbazole skeleton (Japanese Laid-Open Patent Application 54-14967);phthalocyanine pigments such as C.I. Pigment Blue 16 (C.I. 74100);indigo pigments such as C.I. Vat Brown 5 (C.I. 73410) and C.I. Vat Dye(C.I. 73030); and perylene pigments such as Algol Scarlet B andIndanthrene Scarlet R (made by Bayer Co., Ltd.). These charge generationmaterials may be used alone or in combination.

When the electrophotographic photoconductor of the present inventioncomprises a phthalocyanine pigment as the charge generation material,the sensitivity and durability of the obtained photoconductor areremarkably improved. In this case, there can be employed aphthalocyanine pigment having a phthalocyanine skeleton represented bythe following formula:

In the above formula, M (central atom) is a metal atom or a hydrogenatom.

To be more specific, as the central atom (M) in the formula, there canbe employed an atom of H, Li, Be, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr,Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd,In, Sn, Sb, Ba, Hf, Ta, W, Re, Os, Ir, Pt, Au, Mg, Ti, La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Pa, U, Np or Am; thecombination of two or more atoms constituting an oxide, chloride,fluoride, hydroxide or bromide. The central atom is not limited to theabove-mentioned atoms.

The above-mentioned phthalocyanine pigment for use in the presentinvention, which has at least the basic structure as indicated by theabove-mentioned formula, may have a dimer structure or trimer structure,and further, a polymeric structure. Further, the basic structure of theabove-mentioned formula may have a substituent.

Of the phthalocyanine compounds represented by the aforementionedformula, an oxotitanium phthalocyanine compound which has the centralatom (M) of TiO in the above formula, and a metal-free phthalocyaninecompound which has a hydrogen atom as the central atom (M) areparticularly preferred in the present invention because the obtainedphotoconductors show excellent photoconductive properties.

In addition, it is known that each phthalocyanine compound has a varietyof crystal systems. For example, the above-mentioned oxotitaniumphthalocyanine has crystal systems of α-type, β-type, γ-type, m-type,and y-type. In the case of copper phthalocyanine, there are crystalsystems of α-type, β-type, and γ-type. The properties of thephthalocyanine compound vary depending on the crystal system thereofalthough the central metal atom is the same. According to the report of“Electrophotography —the Society Journal— Vol. 29, No. 4 (1990)”, theproperties of the photoconductor vary depending on the crystal system ofa phthalocyanine contained in the photoconductor. In light of thedesired photoconductive properties, therefore, it is important to selectthe phthalocyanine in the optimal crystal system. The oxotitaniumphthalocyanine in the y-type crystal system is particularlyadvantageous.

The above-mentioned charge generation materials with phthalocyanineskeleton may be used in combination in the charge generation layer.Further, such charge generation materials with phthalocyanine skeletonmay be used in combination with other charge generation materials. Inthis case, inorganic and organic conventional charge generationmaterials can be employed.

Specific examples of the inorganic charge generation material arecrystalline selenium, amorphous selenium, selenium—tellurium,selenium—tellurium—halogen, selenium—arsenic compound, and a-silicon(amorphous silicon). In particular, when the above-mentioned a-siliconis employed as the charge generation material, it is preferable that thedangling bond be terminated with hydrogen atom or a halogen atom, or bedoped with boron atom or phosphorus atom.

Specific examples of the organic charge generation material which can beused in combination with the phthalocyanine compound are azulenium saltpigment, squaric acid methyne pigment, azo pigment having a carbazoleskeleton, azo pigment having a triphenylamine skeleton, azo pigmenthaving a diphenylamine skeleton, azo pigment having a dibenzothiopheneskeleton, azo pigment having a fluorenone skeleton,. azo pigment havingan oxadiazole skeleton, azo pigment having a bisstilbene skeleton, azopigment having a distyryl oxadiazole skeleton, azo pigment having adistyryl carbazole skeleton, perylene pigment, anthraquinone pigment,polycyclic quinone pigment, quinone imine pigment, diphenylmethanepigment, triphenylmethane pigment, benzoquinone pigment, naphthoquinonepigment, cyanine pigment, azomethine pigment, indigoid pigment, andbisbenzimidazole pigment.

The electrophotographic photoconductor shown in FIG. 3 can be fabricatedby the following method:

To provide the charge generation layer 5 on the electroconductivesupport 1, the charge generation material is vacuum-deposited on theelectroconductive support 1. Alternatively, the finely-divided particlesof the charge generation material 3 are dispersed in an appropriatesolvent, together with the binder agent when necessary, so that acoating liquid for the charge generation layer 5 is prepared. The thusprepared coating liquid is coated on the electroconductive support 1 anddried, whereby the charge generation layer 5 is formed on theelectroconductive support 1. The charge generation layer 5 may besubjected to surface treatment by buffing and adjustment of thethickness thereof if required. On the thus formed charge generationlayer 5, a coating liquid in which at least one aromatic poly-carbonateresin with the charge transporting properties according to the presentinvention, optionally in combination with a binder agent is dissolved iscoated and dried, so that the charge transport layer 4 is formed on thecharge generation layer 5. In the charge generation layer 5, the samecharge generation materials as employed in the above-mentionedphotoconductive layer 2 a can be used.

The thickness of the charge generation layer 5 is 5 μm or less,preferably 2 μm or less. It is preferable that the thickness of thecharge transport layer 4 be in the range of 3 to 50 μm, more preferablyin the range of 5 to 40 μm.

When the charge generation layer 5 is provided on the electroconductivesupport 1 by coating the dispersion in which finely-divided particles ofthe charge generation material 3 are dispersed in an appropriatesolvent, it is preferable that the amount of finely-divided particles ofthe charge generation material 3 for use in the charge generation layer5 be in the range of 10 to 100 wt. %, more preferably in the range ofabout 50 to 100 wt. % of the total weight of the charge generation layer5. It is preferable that the amount of aromatic polycarbonate resin ofthe present invention 4 be in the range of 40 to 100 wt. % of the totalweight of the charge transport layer 4.

As previously mentioned, the photoconductive layer 2 b may comprise alow-molecular weight charge transport material.

Examples of the low-molecular weight charge transport material for usein the present invention are as follows: oxazole derivatives, oxadiazolederivatives (Japanese Laid-Open Patent Applications 52-139065 and52-139066), imidazole derivatives, triphenylamine derivatives (JapaneseLaid-Open Patent Application 3-285960), benzidine derivatives (JapanesePatent Publication 58-32372), α-phenylstilbene derivatives (JapaneseLaid-Open Patent Application 57-73075), hydrazone derivatives (JapaneseLaid-Open Patent Applications 55-154955, 55-156954, 55-52063, and56-81850), triphenylmethane derivatives (Japanese Patent Publication51-10983), anthracene derivatives (Japanese Laid-Open Patent Application51-94829), styryl derivatives (Japanese Laid-Open Patent Applications56-29245 and 58-198043), carbazole derivatives (Japanese Laid-OpenPatent Application 58-58552), and pyrene derivatives (Japanese Laid-OpenPatent Application 2-94812).

To fabricate the photoconductor as shown in FIG. 4, a coating liquid forthe protective layer 6 is prepared by dissolving the aromaticpolycarbonate resin of the present invention, optionally in combinationwith the binder agent, in a solvent, and the thus obtained coatingliquid is coated on the charge transport layer 4 of the photoconductorshown in FIG. 3, and dried.

It is preferable that the thickness of the protective layer 6 be in therange of 0.15 to 10 μm. It is preferable that the amount of aromaticpolycarbonate resin of the present invention for use in the protectivelayer 6 be in the range of 40 to 100 wt. % of the total weight of theprotective layer 6.

The electrophotographic photoconductor as shown in FIG. 5 can befabricated by the following method:

The aromatic polycarbonate resin of the present invention, optionally incombination with the binder agent, is dissolved in a solvent to preparea coating liquid for the charge transport layer 4. The thus preparedcoating liquid is coated on the electroconductive support 1 and dried,whereby the charge transport layer 4 is provided on theelectroconductive support 1. On the thus formed charge transport layer4, a coating liquid prepared by dispersing the finely-divided particlesof the charge generation material 3 in a solvent in which the binderagent may be dissolved when necessary, is coated by spray coating anddried, so that the charge generation layer 5 is provided on the chargetransport layer 4. The amount ratios of the components contained in thecharge generation layer 5 and charge transport layer 4 are the same asthose previously described in the description of FIG. 3.

When the protective layer 6 is formed on the above prepared chargegeneration layer 5 in the same manner as mentioned in the description ofFIG. 4, the electrophoto-graphic photoconductor with such a structure asshown in FIG. 6 can be fabricated.

To fabricate any of the aforementioned photoconductors of the presentinvention, a metallic plate or foil made of aluminum, a plastic film onwhich a metal such as aluminum is deposited, and a sheet of paper whichhas been treated so as to be electroconductive can be employed as theelectroconductive support 1.

Specific examples of the binder agent used in the preparation of thephotoconductor according to the present invention are condensationresins such as polyamide, polyurethane, polyester, epoxy resin,polyketone and polycarbonate; and vinyl polymers such aspolyvinylketone, polystyrene, poly-N-vinylcarbazole and polyacrylamide.All the resins that have electrically insulating properties and adhesionproperties can be employed.

Some plasticizers may be added to the above-mentioned binder agent, whennecessary. Examples of the plasticizer for use in the present inventionare halogenated paraffin, dimethylnaphthalene and dibutyl phthalate.Further, a variety of additives such as an antioxidant, a lightstabilizer, a thermal stabilizer and a lubricant may also be containedin the binder agent when necessary.

Furthermore, in the electrophotographic photoconductor according to thepresent invention, an intermediate layer such as an adhesive layer or abarrier layer may be interposed between the electroconductive supportand the photoconductive layer when necessary.

Examples of the material for use in the intermediate layer arepolyamide, nitrocellulose, aluminum oxide and titanium oxide. It ispreferable that the thickness of the intermediate layer be 1 μm or less.

When copying is performed by use of the photoconductor according to thepresent invention, the surface of the photoconductor is uniformlycharged to a predetermined polarity in the dark. The uniformly chargedphotoconductor is exposed to a light image so that a latentelectrostatic image is formed on the surface of the photoconductor. Thethus formed latent electrostatic image is developed to a visible imageby a developer, and the developed image can be transferred to a sheet ofpaper when necessary.

The photosensitivity and the durability of the electrophotographicphotoconductor according to the present invention are remarkablyimproved.

Other features of this invention will become apparent in the course ofthe following description of exemplary embodiments, which are given forillustration of the invention and are not intended to be limitingthereof.

SYNTHESIS EXAMPLE 1

[Synthesis of Stilbene Compound]

7.59 g (0.002 mol) of N,N-bis(3-hydroxyphenyl)stilbene-4-amine, 22.44 g(0.12 mol) of m-bromoanisole, 22.12 g (0.16 mol) of potassium carbonate,and 1.26 g of activated copper powder were added to 40 ml ofnitrobenzene, and the above prepared mixture was stirred for 4 hours at170° C. in a stream of nitrogen.

Thereafter, the reaction mixture was allowed to stand at roomtemperature, and 200 ml of toluene was added to the reaction mixture.The resulting insoluble material was removed from the reaction mixtureby filtration, and the solvent was distilled away from the reactionmixture under reduced pressure, whereby 10.3 g of a black oily materialwas obtained.

This oily material was chronatographed on silica gel and eluted with amixed solvent of toluene and n-hexane (at a ratio by volume of 2:1), sothat N,N-bis[3-(3-methoxyphenoxy)phenyl]stilbene-4-amine represented bythe following formula was obtained as a light yellow oily material in ayield of 9.0 g.

The results of the elemental analysis of the thus obtained product wereas follows:

% C % H % N Found 81.44 5.70 2.39 Calculated 81.20 5.62 2.37

NMR (CDCl₃); δ 3.76 (S 6EH, OCH₃x2)

SYNTHESIS EXAMPLE 2

[Synthesis of Diol Compound]

A mixture of 1.60 g (0.02 mol) of the stilbene compound synthesized inSynthesis Example 1, and 10.0 g (0.11 mol) of sodium thioethoxide wasadded to 180 ml of dry N,N-dimetylformamide and refluxed for 2.5 hoursin a stream of nitrogen.

Then, the reaction mixture was allowed to stand at room temperature, andpoured into 350 ml of water. The reaction mixture was neutralized withconcentrated hydrochloric acid. The resultant precipitate was extractedwith ethyl acetate, and the thus obtained organic layer was washed withwater and the solvent was distilled away from the reaction mixture,thereby obtaining a brown oily material.

This material was chromatographed on silica gel and eluted with a mixedsolvent of toluene and ethyl acetate (at a ratio by volume of 5:1), sothat N,N-bis[3-(3-hydroxyphenoxy)phenyl]stilbene-4-amine represented bythe following formula was obtained as colorless crystals in the form ofneedles in a yield of 8.27 g.

The melting point of this diol compound was 126.3° C. (endothermic peakby TG-DTA).

The results of the elemental analysis of the thus obtained product wereas follows:

% C % H % N Found 80.90 5.24 2.51 Calculated 80.96 5.20 2.49

FIG. 7 is an infrared spectrum of the above prepared diol by use of aKBr tablet.

EXAMPLE 1-1

[Synthesis of Aromatic Polycarbonate Resin No. 1]

2.50 parts of a diol with the charge transporting properties, that is,N,N-bis[3-(3-hydroxyphenoxy)phenyl]-stilbene-4-amine synthesized inSynthesis Example 2, 1.87 parts of a copolymerizable diol, that is,2,2-bis(4-hydroxyphenyl)propane, and 0.0155 parts of a molecular weightmodifier, that is, 4-tert-butylphenol were placed in a reactioncontainer with stirrer.

With the addition of an aqueous solution prepared by dissolving 2.61parts of sodium hydroxide and 0.046 parts of sodium hydrosulfite in 30.7parts of water, the obtained reaction mixture was dissolved withstirring in a stream of nitrogen under the application of heat thereto.

Thereafter, the reaction mixture was cooled to 20° C. and vigorouslystirred, with a solution prepared by dissolving 1.50 parts ofbis(trichloromethyl)-carbonate, that is a trimer of a phosgene, in 25.6parts of dichloromethane being added to the reaction mixture, wherebythe polymerization reaction was carried out as the emulsion was formed.

The reaction mixture was then stirred for 15 minutes at roomtemperature. With the addition of 0.0064 parts of triethylamine, thereaction mixture was further stirred for 60 minutes at room temperature.Then, a solution prepared by dissolving 0.10 parts of phenylchloroformate in 5 parts of dichloromethane was added to the reactionmixture, and the resultant mixture was stirred for 120 minutes at roomtemperature.

Thereafter, by the addition of 250 parts of dichloromethane to thereaction mixture, an organic layer was separated. The resultant organiclayer was successively washed with a 3% aqueous solution of sodiumhydroxide, a 2% aqueous solution of hydrochloric acid, and water.

The thus obtained organic layer was added dropwise to large quantitiesof methanol, whereby a white polycarbonate resin was precipitated.

Thus, a polycarbonate resin No. 1 (in the form of a random copolymer)according to the present invention was obtained.

The structural units for use in the polycarbonate resin are shown inTABLE 1 and the moiety ratio of each structural unit is put beside thestructural unit in TABLE 1.

TABLE 1 also shows the results of the elemental analysis of the obtainedpolycarbonate resin. The polycarbonate resin was identified as apolycarbonate random copolymer comprising the above-mentioned structuralunits through the elemental analysis.

The glass transition temperature (Tg) of the above obtained aromaticpolycarbonate resin No. 1 was 120.9° C. when measured by use of adifferential scanning calorimeter.

The polystyrene-reduced number-average molecular weight (Mn) andweight-average molecular weight (Mw), which were measured by the gelpermeation chromatography, were respectively 70,287 and 133,089.

FIG. 8 shows an infrared spectrum of the aromatic polycarbonate resinNo. 1, measured by the thin film method.

EXAMPLES 1-2 and 1-3

[Synthesis of aromatic polycarbonate resins No. 2 and No. 3]

The procedure for preparation of the aromatic polycarbonate resin No. 1in Example 1-1 was repeated except that 2,2-bis(4-hydroxyphenyl)propaneemployed in Example 1-1 was replaced by the respective diol compounds asshown in TABLE 1, and the amount ratios between the two diols wererespectively changed.

Thus, aromatic polycarbonate resins No. 2 and No. 3 according to thepresent invention were obtained. The structure of each polycarbonateresin is shown in TABLE 1.

The results of the elemental analysis, the polystyrene-reducednumber-average molecular weight (Mn) and weight-average molecular weight(Mw), and the glass transition temperature (Tg) of each polycarbonateresin are also shown in TABLE 1.

Infrared spectra of the aromatic polycarbonate resins No. 2 and No. 3,measured by the thin film method, are respectively shown in FIGS. 9 and10.

TABLE 1 Elemental Analysis Molecular % C % H % N Example PolycarbonateWeight Found Found Found No. Resin No. Structure of Polycarbonate ResinMn Mw (Calcd.) (Calcd.) (Calcd.) Tg (° C.) 1-1 1

70287 133089 77.58 (77.73) 5.12 (5.03) 1.28 (1.32) 120.9 1-2 2

32608 125338 78.24 (78.17) 5.39 (5.42) 1.31 (1.32) 128.9 1-3 3

44525 174240 78.49 (78.59) 5.28 (5.30) 1.35 (1.32) 114.2

EXAMPLE 2-1

[Fabrication of Photoconductor No. 1]

(Formation of intermediate layer)

A commercially available polyamide resin (Trademark “C-8000”, made byToray Industries, Inc.) was dissolved in a mixed solvent of methanol andbutanol, so that a coating liquid for an intermediate layer wasprepared.

The thus prepared coating liquid was coated on an aluminum plate by adoctor blade, and dried at room temperature, so that an intermediatelayer with a thickness of 0.3 μm was provided on the aluminum plate.

(Formation of charge generation layer)

A coating liquid for a charge generation layer was prepared bypulverizing and dispersing a bisazo compound of the following formula,serving as a charge generation material, in a mixed solvent ofcyclohexanone and 2-butanone using a ball mill. The thus obtainedcoating liquid was coated on the above prepared intermediate layer by adoctor blade, and dried at room temperature.

Thus, a charge generation layer with a thickness of 0.5 μm was formed onthe intermediate layer.

(Formation of charge transport layer)

The aromatic polycarbonate resin No. 1 of the present invention preparedin Example 1-1, serving as a charge transport material, was dissolved indichloromethane, so that a coating liquid for a charge transport layerwas prepared. The thus obtained coating liquid was coated on the aboveprepared charge generation layer by a doctor blade, and dried at roomtemperature and then at 120° C. for 20 minutes, so that a chargetransport layer with a thickness of 20 μm was provided on the chargegeneration layer.

Thus, an electrophotographic photoconductor No. 1 according to thepresent invention was fabricated.

EXAMPLES 2-2 and 2-3

The procedure for fabrication of the electrophotographic photoconductorNo. 1 in Example 2-1 was repeated except that the aromatic polycarbonateresin No. 1 for use in the charge transport layer coating liquid inExample 2-1 was replaced by the aromatic polycarbonate resins No. 2 andNo. 3 synthesized in Examples 1-2 and 1-3, respectively.

Thus, electrophotographic photoconductors No. 2 and No. 3 according tothe present invention were fabricated.

Each of the electrophotographic photoconductors No. 1 to No. 3 accordingto the present invention respectively fabricated in Examples 2-1 to 2-3was charged negatively in the dark under application of −6 kV of coronacharge for 20 seconds, using a commercially available electrostaticcopying sheet testing apparatus (“Paper Analyzer Model SP-428” made byKawaguchi Electro Works Co., Ltd.). The surface potential (Vm) of eachphotoconductor was measured.

Then, each electrophotographic photoconductor was allowed to stand inthe dark for 20 seconds without applying any charge thereto, and thesurface potential (Vo) of the photoconductor was measured.

Each photoconductor was then illuminated by a tungsten lamp in such amanner that the illuminance on the illuminated surface of thephotoconductor was 4.5 lux, and the exposure E_(½) (lux•sec) required toreduce the initial surface potential Vo (V) to ½ the initial surfacepotential Vo (V) was measured.

The results are shown in TABLE 2.

TABLE 2 Poly- Example carbonate −Vm −Vo E_(½) No. Resin No. (V) (V) (lux· sec) 2-1 No. 1 1546 1332 1.34 2-2 No. 2 1517 1323 1.60 2-3 No. 3 15341327 1.40

Furthermore, each of the above obtained electrophotographicphotoconductors No. 1 to No. 3 was set in a commercially availableelectrophotographic copying machine, and the photoconductor was chargedand exposed to light images via the original images to form latentelectrostatic images thereon. Then, the latent electrostatic imagesformed on the photoconductor were developed into visible toner images bya dry developer, and the visible toner images were transferred to asheet of plain paper and fixed thereon. As a result, clear toner imageswere obtained on the paper. When a wet developer was employed for theimage formation, clear images were formed on the paper similarly.

The previously mentioned aromatic polycarbonate resin of the presentinvention, which is remarkably effective as the photoconductive materialfor use in the electrophotographic photoconductor, is optically orchemically sensitized with a sensitizer such as a dye or Lewis acid. Inparticular, the polycarbonate resin can effectively function as thecharge transport material in the function-separating typeelectrophotographic photoconductor.

The above-mentioned polycarbonate resin is provided with the chargetransporting properties. Therefore, the photosensitivity and durabilityof the photoconductor can be improved when the aforementionedpolycarbonate resin is contained in the photoconductive layer.

Japanese Patent Applications No. 09-162642 and No. 09-162667 filed Jun.19, 1997 are hereby incorporated by reference.

What is claimed is:
 1. An aromatic polycarbonate resin comprising astructural unit of formula (I):

wherein Ar¹, Ar², Ar³ and Ar⁴ are each an arylene group which may have asubstituent; Ar⁵ is an aryl group which may have a substituent; and R¹is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which mayhave a substituent, or an aryl group which may have a substituent. 2.The polycarbonate resin as claimed in claim 1, wherein said structuralunit of formula (I) is represented by formula (III):

wherein Ar⁵ and R¹ are respectively the same as defined in formula (I).3. The polycarbonate resin as claimed in claim 2, wherein saidstructural unit of formula (III) is represented by formula (IV):


4. An aromatic polycarbonate resin comprising a structural unit offormula (I) structural unit of formula (II), with a composition ratio ofsaid structural unit of formula (I) to said structural unit of formula(II) satisfying a relationship of 0<k/(k+j)≦1, wherein k is a moietyratio of said structural unit of formula (I) and j is a moiety ratio ofsaid structural unit of formula (II):

wherein Ar¹, Ar², Ar³ and Ar⁴ are each an arylene group which may have asubstituent; Ar⁵ is an aryl group which may have a substituent; R¹ is ahydrogen atom, an alkyl group having 1 to 4 carbon atoms which may havea substituent, or an aryl group which may have a substituent; and X is abivalent aliphatic group, a bivalent cyclic aliphatic group, a bivalentaromatic group, a bivalent group obtained by bonding said bivalentgroups, or

in which R², R³, R⁴ and R⁵ are each independently an alkyl group whichmay have a substituent, an aryl group which may have a substituent, or ahalogen atom; a and b are each independently an integer of O to 4; c andd are each independently an integer of 0 to 3; and m is an integer of 0or 1, provided that when m=1, Y is a straight-chain alkylene grouphaving 2 to 12 carbon atoms, —O—, —S—, —SO—, —SO₂—, —CO—,

in which Z¹ and Z² are each a bivalent aliphatic group which may have asubstituent or an arylene group which may have a substituent; and R⁶,R⁷, R⁸, R⁹, R¹⁰, R¹¹ and R¹² are each independently a hydrogen atom, ahalogen atom, an alkyl group having 1 to 5 carbon atoms which may have asubstituent, an alkoxyl group having 1 to 5 carbon atoms which may havea substituent, or an aryl group which may have a substituent, and R⁶ andR⁷ may form a carbocyclic ring or heterocyclic ring having 6 to 12carbon atoms together, or may form a carbocyclic ring or heterocyclicring in combination with R² and R³; p and q are each an integer of 0 or1, provided that when p and q represent 1, R¹³ and R¹⁴ are each analkylene group having 1 to 4 carbon atoms; R¹⁵ and R¹⁶ are eachindependently an alkyl group having 1 to 5 carbon atoms which may have asubstituent, or an aryl group which may have a substituent; e is aninteger of 0 to 4; f is an integer of 0 to 20; and g is an integer of 0to
 2000. 5. The polycarbonate resin as claimed in claim 4, wherein saidstructural unit of formula (I) is represented by formula (III):

wherein Ar⁵ and R¹ are respectively the same as defined in formula (I).6. The polycarbonate resin as claimed in claim 5, wherein saidstructural unit of formula (III) is represented by formula (IV):